Cannizzaro reaction

Stanislao Cannizzaro, FRS was an Italian chemist. He is remembered today largely for the Cannizzaro reaction and for his influential role in the atomic-weight deliberations of the Karlsruhe Congress in 1860.-Biography:...

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

lacking a hydrogen atom in the alpha position. Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol

Benzyl alcohol

Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor...

Benzoic acid , C7H6O2 , is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. Its salts are used as a food preservative and benzoic acid is an important precursor for the synthesis...

Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

Stanislao Cannizzaro, FRS was an Italian chemist. He is remembered today largely for the Cannizzaro reaction and for his influential role in the atomic-weight deliberations of the Karlsruhe Congress in 1860.-Biography:...

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

lacking a hydrogen atom in the alpha position. Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol

Benzyl alcohol

Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor...

Benzoic acid , C7H6O2 , is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. Its salts are used as a food preservative and benzoic acid is an important precursor for the synthesis...

Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

. For aldehydes with a hydrogen atom alpha to the carbonyl, i.e. RCHR'CHO, the preferred reaction is an aldol condensation

Aldol condensation

An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone....

, originating from deprotonation of this hydrogen. Reviews have been published.

Variations

A special condition is the crossed Cannizzaro reaction. This variation is more common these days because the original Cannizzaro reaction yields a mixture of alcohol and carboxylic acid. For example any aldehyde with no alpha hydrogens can be reduced when in the presence of formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...

and the corresponding alcohol is obtained in a high yield although the atom economy

Atom economy

Atom economy describes the conversion efficiency of a chemical process in terms of all atoms involved . In an ideal chemical process, the amount of starting materials or reactants equals the amount of all products generated and no atom is wasted...

is still low.

Scope

A solvent-free reaction has been reported involving mixing 2-chlorobenzaldehyde with potassium hydroxide

Potassium hydroxide

Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

A mortar and pestle is a tool used to crush, grind, and mix solid substances . The pestle is a heavy bat-shaped object, the end of which is used for crushing and grinding. The mortar is a bowl, typically made of hard wood, ceramic or stone...

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See also

The Meerwein-Ponndorf-Verley Reduction in organic chemistry is the reduction of ketones and aldehydes to their corresponding alcohols utilizing aluminumalkoxide catalysis in the presence of a sacrificial alcohol...

Oppenauer oxidation, named after Rupert Viktor Oppenauer, is a gentle method for selectively oxidizing secondary alcohols to ketones.The reaction is the opposite of Meerwein-Ponndorf-Verley reduction. The alcohol is oxidized with aluminium isopropoxide in excess acetone...

The Tishchenko reaction is a chemical reaction that involves disproportionation of an aldehyde lacking a hydrogen atom in the alpha position in the presence of an alkoxide. The reaction product is an ester. Catalysts are aluminium alkoxides or sodium alkoxides...